1. Field of the Invention
The present invention is directed to a process for the production of etched structures in a surface of solid bodies by ionic etching utilizing a mask on the surface which mask, along with the solid body, disintegrates and is removed by the ion bombardment of the ionic etching process.
2. Prior Art.
Depressions of a given form can be obtained in a surface of a solid body through bombardment with energetic ions and such a process is suggested in Journal of Materials Science, Vol. 4 (1969) pg, 56. In such a process, the material of the solid body is removed by virtue of atomic collision between the oncoming ions and the components of the solid body. During this process, the rate of removal of the area exposed to the ion bombardment is dependent upon factors such as the mass and energy of the ions, the mass of the components of the solid body, and upon the direction of incidence of the ion beam (see Journal of Applied Physics, Vol 30 (1959) pg. 1762);
In U.S. Pat. Nos. 3,860,783 and 3,839,177, etching masks are used during the ionic etching to produce a given structure in the surface of the solid body and the etching mask may be a film of photosensitive lacquier applied to a surface of the solid body. The desired pattern of the mask is obtained with a photolithographic process. The parts of the surface of the solid body which are not covered by the film of photosensitive lacquer are then etched away by the ion bombardment (ionic etching) and during the course of the ion bombardment, the edge profile or shape of the etching mask is produced in the surface of the solid body.
During ionic etching, the photosensitive lacquer etching mask is itself attacked by the ion bombardment. This attack on the mask causes the etching process to produce depressions in the surface of the solid body which depressions have faces or edge surfaces which do not extend at right angles to the surface of the solid body but have a slope of about 60.degree. relative to the surface of the solid body. Since layers of material are subsequently applied to the etched body, this result on one hand is desired because the subsequently applied layer will adhere better to the edges that are not too steep and exhibit a better distribution of thickness than those layers disposed on edges which extend at right angles to the surface of the solid body. On the other hand, the photo lacquer mask is worn away during the ionic etching and is thus reduced in size. This reduction in the size of the mask will result in the structure being etched in the surface of the solid body by ion bombardment having a larger size or area than the corresponding structures of photo lacquer mask. This phenomena can only be compensated for to a limited extent by making dimensional allowances in the photosensitive lacquer mask because in the case of structures produced in a photosensitive lacquer coating with a photolithographic process one cannot go below a minimum distance because of diffraction phenomena arising during optical projections.
A dimensional loss in the photosensitive lacquer mask during an ionic etching process can be avoided to some extent if metallic masks are used and a reactive gas, which reduces the etching rates of the metallic mask is added to the surrounding atmosphere during the ionic etching process. However, with this solution the ionic etching will no longer produce the sloped edges of about 60.degree. but will produce edges extending virtually at right angles to the surface being etched. This edge configuration will produce several disadvantages. For example, when the etched structure is to be subsequently uniformly coated by vapor deposition, the vapor deposited coating will often become detached at the vertical edges of the etched structure.